The present invention generally relates to address data accessing devices in reproducing apparatuses which reproduce recorded signals from a rotary recording medium, and more particularly to an address data accessing device which selectively transmits an address data which is used to search for recorded positions of first and second information signals which are recorded on a rotary recording medium (hereinafter simply referred to as a disc), to a pickup device within the reproducing apparatus in accordance with an instruction from a main reproducing apparatus body.
An electrostatic capacitance type disc (so-called video disc) and a reproducing apparatus for reproducing recorded signals from such a disc have been proposed and reduced to practice. In such a disc, a color video signal and an audio signal are recorded on a spiral track as variations in geometrical configuration. Further, reference signals for tracking control are recorded on both sides of the spiral track. The disc is scanned by a reproducing stylus which has an electrode. Since the electrostatic capacitance between the electrode of the reproducing stylus and the disc varies according to the variations in the geometrical configuration on the disc, the recorded signals are reproduced from the disc by detecting the variations in the above electrostatic capacitance.
On the other hand, an electrostatic capacitance type digital audio disc has been proposed and reduced to practice. In such a digital audio disc, the information signal is recorded similarly as in the case of the video disc. However, in the digital audio disc, a digital audio signal is recorded as the information signal, instead of the color video signal and the audio signal which are recorded on the video disc. The digital audio signal is obtained by subjecting an audio signal to a digital pulse modulation such as a pulse code modulation (PCM). The only differences between the digital audio disc and the video disc are the different information signals which are recorded, and the different formats of the recorded signals which are employed. Aside from these differences, the recorded signals are reproduced from the digital audio disc in the same manner as in the case of the video disc. In other words, the recorded signals are reproduced by detecting the variations in the electrostatic capacitance, and the tracking control is carried out by reproducing reference signals because there is no groove formed on the disc for guiding the reproducing stylus. The diameter of the digital audio disc and the rotational speed of the digital audio disc at the time of reproduction are also the same as those employed in the video disc. Due to these similarities between the digital audio disc and the video disc, the digital audio disc can be played in a video disc reproducing apparatus (video disc player), by modifying a part of the video disc player. In reality, it becomes possible to play the digital audio disc in an existing video disc player, by coupling an adapter which includes an address data accessing device to this existing video disc player.
The digital audio disc has a recording capacity to record signals of up to four channels. There are the following four ways of utilizing the four channels which can be recorded on the digital audio disc: (a) to record digital audio signals of three channels and a digital video signal of one channel; (b) to record digital audio signals of four channels; (c) to record a first 2-channel stereo digital audio signal and a second 2-channel stereo digital audio signal (that is, to record two kinds of 2-channel digital audio signals); and (d) to record digital audio signals of two channels and digital video signals which are transmitted in two channels. The disc player must be designed so that a disc which is recorded with any of the above four signal combinations can be played.
When the disc player plays a disc which is recorded with the signals under (a) above, it is possible to listen to sounds which are generated through three speakers while watching a still picture which is reproduced on a television receiver as a supplementary information to the audio program. On the other hand, when the disc player plays the disc which is recorded with the signals under (b) above, it is possible to listen to 4-channel stereo sounds which are generated through four speakers. It is possible to listen to 2-channel stereo sounds which are generated through two speakers by selecting one of the two 2-channel digital audio signals which are recorded, when playing a disc which is recorded with the signals under (c) above. Further, when playing a disc which is recorded with the signals under (d) above, it is possible to listen to sounds which are generated through two speakers while watching a reproduced picture which is selected from the digital video signals which are recorded in the two channels.
The digital audio disc is also recorded with an address signal. This address signal indicates the recorded position (track position) of the information signal, and is used when searching for a predetermined recorded position of the information signal during a mode such as a random access mode. Hence, the adapter described before includes the address data accessing device which detects the address signal and transmits the detected address signal to the video disc player.
When the disc is recorded with the signals under (c) above, it is necessary to select one of the first and second 2-channel digital audio signals which are recorded on the disc at the time of a normal reproduction mode. Modes in which the first and second 2-channel digital audio signals are selected, are referred to as select modes A and B, respectively.
However, the previously devised address data accessing device had a disadvantage in that it was impossible to search for a program having a desired chapter number and start the reproduction from the desired chapter number, as will be described later on in the specification. This disadvantage was introduced because an address data fetch circuit does not fetch a reproduced chapter address data at the point when a chapter search button of the reproducing apparatus is pushed, when carrying out a search which is based on an address data of a kind different from the mode which is displayed while the normal reproduction is carried out, in either the select mode A or the select mode B. Thus, the reproducing apparatus cannot discriminate the chapter number of the program which is to be searched for. In addition, there was another disadvantage in that the reproducing apparatus may search for and reproduce a program having a chapter number which is subsequent to the last chapter number which was fetched before the chapter search button was pushed.
A differently designed reproducing apparatus was also proposed. According to this reproducing apparatus, the chapter address data at the reproducing position is first fetched at the point when the chapter search button is pushed. Then, an arithmetic operation is performed by using the chapter number which is obtained from the fetched chapter address data and the chapter number which is instructed, to start the reproduction of the music program from the desired chapter number. However, in this reproducing apparatus, the chapter address data must once be reproduced in order to fetch the chapter address data. Thus, there was a disadvantage in that it took a little longer to complete the search.